[jboss-jira] [JBoss JIRA] Commented: (JBRULES-2887) AccumulateNode runs into NPE

[Wolfgang Laun (JIRA)]

    [ https://issues.jboss.org/browse/JBRULES-2887?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12593388#comment-12593388 ] 

Wolfgang Laun commented on JBRULES-2887:
----------------------------------------

Manuel Ortiz:


I've executed several times the SampleAlarmRules scenario and found that the problem in that scenario is the existence of a JoinNode (Node 18) which feeds two nodes, a JoinNode (Node 20) and an AccumlateNode (Node 25, the one in which NPE occurs). I've seen that the child tuples of a join node are interconnected via pointers and that those connections must be updated every time a parent tuple of the join node is modified, via reAddLeft and reAddRight tuple methods. When a JoinNode feeds two or more nodes, the child tuples are interconnected in a ordered way that mixes tuples with different sinks. 

In the SampleAlarmRules scenario, when JoinNode18 is right modified, the CompositeLeftTupleSinkAdapter processes several child tuples, but only the last one is returned and reAddLeft'ed, hence breaking the child tuple relations which it seems necessary to keep rete coherence. After this right modify, the next left modify fails because a child tuple related to one node of the composite sink is used to check the next operation to do in another sink node different from the first one. This leads to a chain of incorrect assertions which ends in the AccumulateNode NPE.



> AccumulateNode runs into NPE
> ----------------------------
>
>                 Key: JBRULES-2887
>                 URL: https://issues.jboss.org/browse/JBRULES-2887
>             Project: Drools
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>          Components: drools-core
>    Affects Versions: 5.1.1.FINAL
>            Reporter: Wolfgang Laun
>            Assignee: Mark Proctor
>            Priority: Critical
>             Fix For: 5.2.0.M1
>
>         Attachments: DroolsTest.java, SampleAlarmRules.drl
>
>
> A rule such as
> rule "average"
> when
>     B( id < 10 )
>     $list: List() from collect ( A() over window:time(10s) )
>            Number( $avg: doubleValue ) from accumulate( A( $id : id ) from $list, average( $id ) )
> then
>     System.out.println( "average = " + $avg );
> end
> runs into a NPE
> Caused by: java.lang.NullPointerException
> 	at org.drools.reteoo.AccumulateNode.getFirstMatch(AccumulateNode.java:967)
> 	at org.drools.reteoo.AccumulateNode.splitList(AccumulateNode.java:920)
> 	at org.drools.reteoo.AccumulateNode.removePreviousMatchesForLeftTuple(AccumulateNode.java:874)
> 	at org.drools.reteoo.AccumulateNode.retractLeftTuple(AccumulateNode.java:205)
> 	at org.drools.reteoo.CompositeLeftTupleSinkAdapter.doPropagateRetractLeftTuple(CompositeLeftTupleSinkAdapter.java:238)
> 	at org.drools.reteoo.CompositeLeftTupleSinkAdapter.propagateRetractLeftTupleDestroyRightTuple(CompositeLeftTupleSinkAdapter.java:138)
> 	at org.drools.reteoo.AccumulateNode.retractLeftTuple(AccumulateNode.java:212)
> 	at org.drools.reteoo.ModifyPreviousTuples.retractTuples(ModifyPreviousTuples.java:111)
> 	at org.drools.reteoo.EntryPointNode.modifyObject(EntryPointNode.java:176)
> 	at org.drools.common.NamedEntryPoint.update(NamedEntryPoint.java:450)
> 	at org.drools.common.NamedEntryPoint.update(NamedEntryPoint.java:361)
> 	at org.drools.base.DefaultKnowledgeHelper.update(DefaultKnowledgeHelper.java:183)
> 	at org.drools.base.DefaultKnowledgeHelper.update(DefaultKnowledgeHelper.java:196)
> 	at event.Rule_launch_0.defaultConsequence(Rule_launch_0.java:7)
> 	at event.Rule_launch_0DefaultConsequenceInvoker.evaluate(Rule_launch_0DefaultConsequenceInvoker.java:33)
> 	at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:913)
> A null Parameter accctx is passed down from retractLeftTuple. 

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